JP4893292B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus having a function of automatically stopping an internal combustion engine (engine) while the vehicle is stopped.

  In recent years, vehicles equipped with automatic engine stop devices (so-called idling stop devices) are increasing for the purpose of reducing fuel consumption and exhaust emissions. For example, when the driver automatically stops the engine when the driver stops the vehicle, and then the driver performs an operation (such as a brake release operation) to start the vehicle. The engine is automatically started.

Further, as described in, for example, Patent Document 1 (Japanese Patent No. 3733660), recent vehicles have no abnormality (failure, deterioration) in control system parts or systems during engine operation. It is equipped with an abnormality diagnosis function for self-diagnosis. For example, abnormality diagnosis of exhaust gas sensors (oxygen sensor, air-fuel ratio sensor, etc.) used in an air-fuel ratio control system is performed, or abnormality diagnosis of a catalyst for purifying exhaust gas, a fuel system, an ignition system, etc. is performed. .
Japanese Patent No. 3733660 (first page)

  In general, in order to accurately perform abnormality diagnosis, it is desirable to perform in a steady operation state, which is a stable engine operation state in which the operation condition is maintained almost constant. Many of them are designed to perform abnormality diagnosis in an idling state that is easy to secure.

  However, in a vehicle equipped with an engine automatic stop device, the engine is automatically stopped when the engine operation state becomes the idle operation state. Therefore, the abnormality diagnosis cannot be performed during the idle operation and the engine is operated. However, depending on the traveling conditions, a steady operation state suitable for performing the abnormality diagnosis does not continue for a long time, and the abnormality diagnosis cannot be performed during traveling. For this reason, it is not possible to sufficiently ensure the frequency of execution of abnormality diagnosis, and even if an abnormality actually occurs, the abnormality may not be detected early.

  In addition, when performing vehicle performance evaluation tests by repeating start, acceleration, deceleration, and stop at a short time interval in a predetermined driving mode that has been determined in advance, it is possible to perform abnormality diagnosis of the exhaust gas sensor during driving. The required steady-state operation time cannot be secured, and the exhaust gas sensor abnormality diagnosis cannot be executed indefinitely. As a result, catalyst abnormality diagnosis and fuel that require the output of the exhaust gas sensor (actual air-fuel ratio detection value) System failure diagnosis cannot be performed (if it is not confirmed that the exhaust gas sensor is normal, it is meaningless to perform catalyst or fuel system abnormality diagnosis).

The present invention has been made in view of such circumstances. Accordingly, the object of the present invention is to diagnose an abnormality of the exhaust gas sensor while traveling (during operation of the internal combustion engine) in a vehicle equipped with a function for automatically stopping the internal combustion engine. The internal combustion engine can ensure the frequency of exhaust gas sensor abnormality diagnosis even in an operation state where the exhaust gas sensor cannot be executed, and can reliably perform exhaust gas sensor abnormality diagnosis even in a performance evaluation test performed in a predetermined driving mode. It is to provide an engine control device.

In order to achieve the above object, an invention according to claim 1 is directed to an exhaust gas sensor provided in an exhaust pipe of an internal combustion engine and to stop the internal combustion engine when a predetermined automatic stop condition is satisfied during operation of the internal combustion engine. In the control apparatus for an internal combustion engine, comprising: an automatic stop control means; and an abnormality diagnosis means for executing an abnormality diagnosis of the exhaust gas sensor when a predetermined abnormality diagnosis execution condition is satisfied during operation of the internal combustion engine. If the abnormality diagnosis of the exhaust gas sensor to be executed before the automatic stop condition is satisfied during the operation of the internal combustion engine has not been executed yet, the automatic stop by the automatic stop control means is prohibited. run the abnormality diagnosis of the exhaust gas sensor in a state in which the engine was allowed to idle operation, to be executed before it when the automatic stop condition during operation of the internal combustion engine is satisfied If the abnormality diagnosis of the serial exhaust gas sensor is completed is obtained so as to allow the automatic stop. In this way, if the operation state in which exhaust gas sensor abnormality diagnosis cannot be performed continues during running, the exhaust gas sensor abnormality diagnosis is performed while the internal combustion engine is idling while prohibiting automatic stop while the vehicle is stopped. Even if an operation state in which exhaust gas sensor abnormality diagnosis cannot be performed continues during traveling (during operation of the internal combustion engine), the frequency of exhaust gas sensor abnormality diagnosis can be ensured and a predetermined predetermined traveling mode can be secured. In the performance evaluation test performed in step 1, the abnormality diagnosis of the exhaust gas sensor can be executed reliably.

  In this case, as described in claim 2, the automatic stop may be permitted when the automatic stop is prohibited and the abnormality diagnosis is completed. In this way, if the automatic stop condition is still satisfied when the abnormality diagnosis is completed, the internal combustion engine can be automatically stopped immediately, and an increase in fuel consumption and emission can be suppressed.

Further, as described in claim 3 , when the automatic stop is prohibited, the abnormality diagnosis execution condition may be switched to a condition that is easily established in the idle operation state. In this way, it is possible to reliably perform abnormality diagnosis when the automatic stop is prohibited and the internal combustion engine is idling.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 which is an internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided downstream of the air cleaner 13. A throttle valve 15 and a throttle opening sensor 16 for detecting the throttle opening are provided on the downstream side of the air flow meter 14. The intake pipe 12 is provided with a bypass passage 25 that bypasses the throttle valve 15, and an idle speed control valve (ISC valve) 26 is provided in the bypass passage 25.

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to the cylinder head of each cylinder. A cooling water temperature sensor 27 that detects the cooling water temperature and a crank angle sensor 28 that detects the engine rotation speed are attached to the cylinder block of the engine 11.

  On the other hand, a catalyst 23 such as a three-way catalyst for reducing CO, HC, NOx and the like in the exhaust gas, a NOx occlusion reduction type catalyst, and the like is provided in the middle of the exhaust pipe 22 of the engine 11. On the downstream side, exhaust gas sensors 24 and 25 (oxygen sensor, air-fuel ratio sensor, etc.) for detecting any one of gas component concentration such as oxygen concentration of exhaust gas, air-fuel ratio, and rich / lean are provided. Needless to say, the present invention can be applied to a configuration in which the exhaust gas sensor 25 is not provided on the downstream side of the catalyst 23.

  The various sensor outputs described above are input to an engine control device (hereinafter referred to as “engine ECU”) 29. The engine ECU 29 is mainly composed of a microcomputer, and executes various control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the spark plug 21 is controlled. The engine ECU 29 feedback-controls the air-fuel ratio of the air-fuel mixture supplied to the engine 11 based on the outputs of the exhaust gas sensors 24 and 25 during engine operation.

  An automatic stop control device (hereinafter referred to as “eco-run ECU”) 30 communicates with the engine ECU 29 as automatic stop control means for controlling automatic engine stop / restart for the purpose of reducing fuel consumption and exhaust emissions. It is provided so that it can. The eco-run ECU 30 is mainly composed of a microcomputer, and when a predetermined automatic stop condition (for example, the brake switch is turned on at idle after warm-up and the vehicle speed is equal to or lower than a predetermined value) is established during engine operation. Then, an automatic stop request (fuel cut request) is output to the engine ECU 29. When the engine ECU 29 receives the automatic stop request from the eco-run ECU 30, the engine ECU 29 immediately executes fuel cut to stop the fuel injection of the fuel injection valve 20 and automatically stop the engine 11. After that, the eco-run ECU 30 detects that an operation (for example, a brake release operation, an accelerator stepping operation, a shift operation to the D range, etc.) for starting the vehicle by the driver is detected, and the restart condition is satisfied. 11 is started, the fuel injection of the fuel injection valve 20 is restarted, and the engine 11 is restarted.

  Furthermore, the engine ECU 29 functions as an abnormality diagnosis means for executing an abnormality diagnosis of a control system component or system when a predetermined abnormality diagnosis execution condition is satisfied during engine operation. The components or systems to be subjected to the abnormality diagnosis are, for example, exhaust gas sensors 24 and 25, catalyst 23, fuel system (fuel injection valve 20, fuel pump, etc.), ignition system (ignition plug 21, ignition coil), and the like.

  In the abnormality diagnosis of the exhaust gas sensors 24 and 25, for example, the presence / absence of a range abnormality, responsiveness abnormality, and cycle abnormality is determined. Here, the range abnormality is an abnormality in which the difference between the maximum value and the minimum value of the output voltage of the exhaust gas sensors 24 and 25 is small, and the responsiveness abnormality is an abnormality in which the responsiveness of the exhaust gas sensors 24 and 25 is deteriorated. Yes, for example, whether the response time until the output voltage of the exhaust gas sensors 24, 25 reverses from rich (or lean) to lean (or rich) is longer than the abnormality determination threshold, and whether or not there is a responsive abnormality May be determined. The period abnormality is an abnormality in which the response period of the exhaust gas sensors 24 and 25 becomes too long. For example, the abnormality occurs next from when the output voltage of the exhaust gas sensors 24 and 25 crosses the rich side (or lean side) determination voltage V. The presence or absence of a cycle abnormality may be determined based on whether or not the time until returning to the same determination voltage V is longer than the abnormality determination threshold value. Needless to say, the abnormality diagnosis of the exhaust gas sensors 24 and 25 may be performed by a method other than the above.

  The abnormality diagnosis of the catalyst 23 and the abnormality diagnosis of the fuel system are performed using the outputs (detected air-fuel ratio) of the exhaust gas sensors 24 and 25. For example, as the catalyst 23 deteriorates, the ratio of the exhaust gas rich component (HC, CO, etc.) and the lean component (NOx, etc.) flowing into the catalyst 23 without being purified increases as it flows out of the catalyst 23. For example, using the characteristic that the response time until the change in the air-fuel ratio on the upstream side of 23 appears as the change in the air-fuel ratio on the downstream side of the catalyst 23 is used, for example, the output (or air-fuel ratio) of the exhaust gas sensor 24 on the upstream side The abnormality of the catalyst 23 depends on whether the response time from when the rich / lean of the feedback correction coefficient) is reversed until the rich / lean of the output of the exhaust gas sensor 25 on the downstream side is reversed is longer than the abnormality determination threshold value. The presence or absence of (deterioration) may be determined. Needless to say, the abnormality diagnosis of the catalyst 23 may be performed by a method other than the above.

  The abnormality diagnosis of the fuel system, for example, monitors the deviation between the actual air-fuel ratio detected by the upstream exhaust gas sensor 24 during the air-fuel ratio feedback control and the target air-fuel ratio, and the deviation does not converge within the normal range. If the state continues for a long time, it may be determined that the fuel system is abnormal. Alternatively, if the air-fuel ratio feedback correction coefficient is stuck to the guard value for a long time, it may be determined that the fuel system is abnormal. It goes without saying that the abnormality diagnosis of the fuel system may be performed by a method other than the above.

  In general, in order to accurately perform abnormality diagnosis, it is desirable to perform in a steady operation state, which is a stable engine operation state in which the operation condition is maintained almost constant. Many of them are designed to perform abnormality diagnosis in an idling state that is easy to secure.

  However, as in this embodiment, in the vehicle with the engine automatic stop function, when the engine operation state becomes the idle operation state, the engine 11 is automatically stopped, so the abnormality diagnosis cannot be performed during the idle operation. Although it is necessary to perform abnormality diagnosis while the engine 11 is running, depending on the traveling conditions, a steady operation state suitable for performing abnormality diagnosis does not last long, and abnormality diagnosis cannot be performed during traveling. appear. For this reason, it is not possible to sufficiently ensure the frequency of execution of abnormality diagnosis, and even if an abnormality actually occurs, the abnormality may not be detected early.

  In addition, when a vehicle performance evaluation test is repeated by repeating start, acceleration, deceleration, and stop at a short time interval in a predetermined driving mode determined in advance, abnormality diagnosis of the exhaust gas sensors 24 and 25 is performed during driving. As a result, it is impossible to secure the time required for the steady operation state to be performed, and the abnormality diagnosis of the exhaust gas sensors 24 and 25 cannot be executed indefinitely. As a result, the output of the exhaust gas sensors 24 and 25 (the detected value of the actual air-fuel ratio) The necessary abnormality diagnosis of the catalyst 23 and the abnormality diagnosis of the fuel system cannot be executed (if the exhaust gas sensors 24 and 25 are not confirmed to be normal, it is meaningless to perform the abnormality diagnosis of the catalyst 23 or the fuel system). A malfunction occurs.

  As a countermeasure, in this embodiment, the engine ECU 29 is still executing an abnormality diagnosis (for example, abnormality diagnosis of the exhaust gas sensors 24 and 25) to be executed before a predetermined automatic stop condition is satisfied during engine operation. If not, automatic stop is prohibited, and the abnormality diagnosis execution condition is switched from the abnormality diagnosis execution condition during traveling to the abnormality diagnosis execution condition during idle operation, and abnormality diagnosis is performed while the engine 11 is idling while the vehicle is stopped. When the abnormality diagnosis is completed, automatic stop is permitted. In this way, if the automatic stop condition is still satisfied when the abnormality diagnosis is completed, the engine 11 can be automatically stopped immediately, and an increase in fuel consumption and emission can be suppressed.

  In addition, a gray zone with a low determination accuracy between the normal determination zone where the determination result of the abnormality diagnosis executed while the engine is running (during driving) is normal and the abnormality determination zone where the abnormality is obvious May belong. For example, when diagnosing abnormality of the responsiveness of the exhaust gas sensors 24 and 25, the response time until the output voltage of the exhaust gas sensors 24 and 25 reverses from rich (or lean) to lean (or rich) is, for example, 2 seconds or less. Is a normal determination zone, a response time of, for example, 4 seconds or more is an abnormality determination zone, and a response time range of 2 to 4 seconds is a gray zone with low determination accuracy.

  Therefore, in this embodiment, when the determination result of the abnormality diagnosis executed while the engine is running (running) belongs to a gray zone with a low determination accuracy between the normal determination zone and the abnormality determination zone, automatic stop is prohibited. Thus, the abnormality diagnosis is performed again while the engine 11 is idling. Also in this case, when the automatic stop is prohibited and the abnormality diagnosis is performed again, the automatic stop is permitted. If the automatic stop condition is still satisfied at that time, the engine 11 is automatically stopped immediately.

  The abnormality diagnosis of the present embodiment described above is executed by the engine ECU 29 according to the abnormality diagnosis routine of FIG. The abnormality diagnosis routine of FIG. 2 is a routine for performing abnormality diagnosis of the exhaust gas sensors 24 and 25. When this routine is started, first, in step 101, the routine waits from the start of the engine 11 until a predetermined time necessary for raising the temperature of the exhaust gas sensors 24, 25 to the active temperature range elapses. Then, when a predetermined time has elapsed from the start of the engine 11, the routine proceeds to step 102, where the activation determination of the exhaust gas sensors 24, 25 is performed. At this time, for example, it is determined whether or not the output voltage of the exhaust gas sensors 24 and 25 is inverted between the rich voltage and the lean voltage, and when the rich / lean inversion is detected, the exhaust gas sensors 24 and 25 are activated. That is confirmed.

  Then, when it is confirmed that the exhaust gas sensors 24 and 25 are activated, the routine proceeds to step 103, where a running exhaust gas sensor abnormality diagnosis routine (not shown) is executed to diagnose abnormality during running (engine operation). When the execution condition is satisfied, the presence / absence of a range abnormality, responsiveness abnormality, and cycle abnormality of the exhaust gas sensors 24 and 25 is determined. Conditions for executing abnormality diagnosis during traveling are, for example, (1) steady operation, (2) air-fuel ratio feedback control, and the like.

  Thereafter, the routine proceeds to step 104, where it is determined whether a predetermined automatic stop condition (for example, the brake switch is turned on at idle after warm-up and the vehicle speed is equal to or lower than a predetermined value) is satisfied during engine operation, If the automatic stop condition is not satisfied, the engine operation is continued, and the abnormality diagnosis of the exhaust gas sensors 24 and 25 is executed when the running abnormality diagnosis execution condition is satisfied.

  Then, when the automatic stop condition is satisfied, the routine proceeds to step 105, where it is determined whether or not the abnormality diagnosis of the exhaust gas sensors 24, 25 is completed during traveling (engine operation), and the abnormality of the exhaust gas sensors 24, 25 is still abnormal. If the diagnosis is not completed, the process proceeds to step 107, and an automatic stop prohibition request is output from the engine ECU 29 to the eco-run ECU 30. After this, even when the automatic stop condition is satisfied, the engine 11 is not automatically stopped, and fuel injection is continued to perform idle operation. During the idling operation, idle speed feedback control for feedback control of the engine speed to the target idle speed is executed, and the air-fuel ratio of the air-fuel mixture supplied to the engine 11 based on the outputs of the exhaust gas sensors 24 and 25 is targeted. Air-fuel ratio feedback control for feedback control to the air-fuel ratio is continued.

  Thereafter, the routine proceeds to step 108, where an exhaust gas sensor abnormality diagnosis routine (not shown) during idle operation is executed, and when the abnormality diagnosis execution condition is satisfied during idle operation, the range abnormality and response of the exhaust gas sensors 24, 25 are satisfied. Determine the presence or absence of sexual abnormality or cycle abnormality. The conditions for executing abnormality diagnosis during idling are, for example, (1) idling speed feedback control, (2) air-fuel ratio feedback control, and the like.

  Then, in the next step 109, it is determined whether or not the abnormality diagnosis of the exhaust gas sensors 24 and 25 is completed during idle operation. If the abnormality diagnosis of the exhaust gas sensors 24 and 25 is not completed during idle operation, Returning to step 103, a running exhaust gas sensor abnormality diagnosis routine (not shown) is executed, and abnormality diagnosis of the exhaust gas sensors 24, 25 is executed when an abnormality diagnosis execution condition is satisfied during traveling (engine operation). To do.

  On the other hand, if it is determined in step 109 that the abnormality diagnosis of the exhaust gas sensors 24 and 25 is completed during the idling operation, the process proceeds to step 110, the automatic stop prohibition request to the eco-run ECU 30 is canceled, and the process proceeds to step 111. It is determined whether or not the automatic stop condition is still satisfied. If the automatic stop condition is not satisfied, the process proceeds to step 112 and the engine operation is continued.

  On the other hand, if the automatic stop condition is still satisfied at the time when the automatic stop prohibition request is released, “Yes” is determined in step 111, the process proceeds to step 113, and the eco-run ECU 30 automatically A stop request (fuel cut request) is output to the engine ECU 29. In the next step 114, the engine ECU 29 stops the fuel injection of the fuel injection valve 20 to automatically stop the engine 11.

  If it is determined in step 105 that the abnormality diagnosis of the exhaust gas sensors 24 and 25 is completed during traveling (engine operation), the process proceeds to step 106, and the determination result of the abnormality diagnosis is a normal determination zone and an abnormality determination zone. If it belongs to the gray zone, the abnormality diagnosis of the exhaust gas sensors 24 and 25 is not completed during traveling (engine operation). In step 107, the engine ECU 29 outputs an automatic stop prohibition request to the eco-run ECU 30 to execute idle operation without automatically stopping the engine 11 even when the automatic stop condition is satisfied. Then, in the next step 108, an exhaust gas sensor abnormality diagnosis routine (not shown) during idle operation is executed, and abnormality diagnosis of the exhaust gas sensors 24, 25 is executed during idle operation. When the abnormality diagnosis is completed, the automatic stop prohibition request to the eco-run ECU 30 is canceled (step 109 → 110), and if the automatic stop condition is still satisfied, the automatic stop request is output and the engine 11 is output. Is automatically stopped (steps 111 → 113 → 114).

  The abnormality diagnosis routine of FIG. 2 is a routine for diagnosing abnormality of the exhaust gas sensors 24, 25, but also for abnormality diagnosis of other control system parts or systems (catalyst 23, fuel system, ignition system, etc.) If the abnormality diagnosis that should be executed before that point is not executed yet when the predetermined automatic stop condition is satisfied, the automatic stop is prohibited and the abnormality diagnosis execution condition is idled from the abnormality diagnosis execution condition during traveling. It is only necessary to switch to the abnormality diagnosis execution condition during driving, execute the abnormality diagnosis while the engine 11 is idling while the vehicle is stopped, and permit the automatic stop when the abnormality diagnosis is completed.

  According to the present embodiment described above, when a predetermined automatic stop condition is satisfied during engine operation and an abnormality diagnosis to be executed before that is not yet executed, automatic stop is prohibited and the engine is stopped. Since the abnormality diagnosis is executed in the state in which the engine 11 is idling, even when the operation state in which the abnormality diagnosis cannot be performed during running (engine operation) continues, the frequency of executing the abnormality diagnosis can be secured and determined in advance. In the performance evaluation test performed in the predetermined driving mode, the abnormality diagnosis can be surely performed.

  Moreover, since automatic stop is permitted when automatic stop is prohibited and abnormality diagnosis is completed, if the automatic stop condition is still satisfied when abnormality diagnosis is completed, immediately The engine 11 can be automatically stopped, and an increase in fuel consumption and emission can be suppressed.

  Further, if the determination result of the abnormality diagnosis performed while the engine is running (running) belongs to a gray zone with a low determination accuracy between the normal determination zone and the abnormality determination zone, automatic stop is prohibited and the engine 11 is idled. Since the abnormality diagnosis is re-executed while the vehicle is in operation, it is possible to satisfy the requirements for improving the accuracy and reliability of abnormality diagnosis in a vehicle equipped with an automatic stop function.

1 is a schematic configuration diagram of an entire engine control system showing an embodiment of the present invention. It is a flowchart which shows the flow of an abnormality diagnosis routine.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 15 ... Throttle valve, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 23 ... Catalyst, 24, 25 ... Exhaust gas sensor, 29 ... Engine ECU ( Abnormality diagnosis means), 30 ... Eco-run ECU (automatic stop control means)

Claims (3)

An exhaust gas sensor provided in an exhaust pipe of the internal combustion engine, automatic stop control means for stopping the internal combustion engine when a predetermined automatic stop condition is satisfied during operation of the internal combustion engine, and predetermined abnormality diagnosis during operation of the internal combustion engine In a control device for an internal combustion engine comprising abnormality diagnosis means for performing abnormality diagnosis of the exhaust gas sensor when an execution condition is satisfied
The abnormality diagnosis means performs automatic stop by the automatic stop control means if abnormality diagnosis of the exhaust gas sensor to be executed before the automatic stop condition is satisfied during operation of the internal combustion engine has not been executed yet. An abnormality diagnosis of the exhaust gas sensor is executed in a state in which the internal combustion engine is idled and prohibited, and an abnormality diagnosis of the exhaust gas sensor to be executed before the automatic stop condition is satisfied during the operation of the internal combustion engine The control device for the internal combustion engine, wherein the automatic stop is permitted when the operation is completed .   2. The internal combustion engine according to claim 1, wherein the abnormality diagnosis unit permits the automatic stop by the automatic stop control unit when the automatic stop is prohibited and the abnormality diagnosis of the exhaust gas sensor is finished. 3. Engine control device.   3. The control device for an internal combustion engine according to claim 1, wherein the abnormality diagnosis unit switches the abnormality diagnosis execution condition to a condition that is easily established in an idle operation state when the automatic stop is prohibited.

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